Correlates of snail shell variation along a unidirectional freshwater gradient in Lithasia geniculata (Haldeman, 1840) (Caenogastropoda: Pleuroceridae) from the Duck River, Tennessee, USA

Minton, Russell L.; Hart, K. C.; Fiorillo, Riccardo A.; Brown, Christopher W.

doi:10.12657/folmal.026.007

Cited by 4 publications

(2 citation statements)

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“…[58, 59]). Therefore, the increase in globularity of the shells in lotic habitats represents maybe an adaptation against habitat specific predators as recently demonstrated for Lithasia geniculata [12]. We conclude that in aquatic gastropods the relationships of shell morphology and habitat are more complex than assumed.…”

Section: Discussionsupporting

confidence: 51%

Testing the adaptive value of gastropod shell morphology to flow: a multidisciplinary approach based on morphometrics, computational fluid dynamics and a flow tank experiment

et al. 2019

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A major question in stream ecology is how invertebrates cope with flow. In aquatic gastropods, typically, larger and more globular shells with larger apertures are found in lotic (flowing water) versus lentic (stagnant water) habitats. This has been hypothetically linked to a larger foot, and thus attachment area, which has been suggested to be an adaptation against risk of dislodgement by current. Empirical evidence for this is scarce. Furthermore, these previous studies did not discuss the unavoidable increase in drag forces experienced by the snails as a consequence of the increased cross sectional area. Here, using Potamopyrgus antipodarum as a study model, we integrated computational fluid dynamics simulations and a flow tank experiment with living snails to test whether 1) globular shell morphs are an adaptation against dislodgement through lift rather than drag forces, and 2) dislocation velocity is positively linked to foot size, and that the latter can be predicted by shell morphology. The drag forces experienced by the shells were always stronger compared to the lift and lateral forces. Drag and lift forces increased with shell height but not with globularity. Rotating the shells out of the flow direction increased the drag forces, but decreased lift. Our hypothesis that the controversial presence of globular shells in lotic environments could be explained by an adaptation against lift rather than drag forces was rejected. The foot size was only predicted by the size of the shell, not by shell shape or aperture size, showing that the assumed aperture/foot area correlation should be used with caution and cannot be generalized for all aquatic gastropod species. Finally, shell morphology and foot size were not related to the dislodgement speed in our flow tank experiment. We conclude that other traits must play a major role in decreasing dislodgement risk in stream gastropods, e.g., specific behaviours or pedal mucus stickiness. Although we did not find globular shells to be adaptations for reducing dislodgement risk, we cannot rule out that they are still flow-related adaptations. For instance, globular shells are more crush-resistant and therefore perhaps adaptive in terms of diminishing damage caused by tumbling after dislodgement or against lotic crush-type predators.Electronic supplementary materialThe online version of this article (10.1186/s40851-018-0119-6) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 51%

Testing the adaptive value of gastropod shell morphology to flow: a multidisciplinary approach based on morphometrics, computational fluid dynamics and a flow tank experiment

et al. 2019

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“…However, the evidence presented in these studies is limited to correlations with environmental factors or examination of allozyme variation unrelated to shell traits, and none provide unequivocal evidence of phenotypic plasticity. Other studies have documented shell variation in Lithasia geniculata, Elimia spp., and Pleurocera acuta that is correlated with environmental factors or stream position, but have not proposed a cause for this variation (Minton et al 2007(Minton et al , 2018Dillon and Robinson 2011;Ross et al 2014;Cazenave and Zanatta 2016).…”

Section: Superfamily Cerithioideamentioning

confidence: 99%

Phenotypic Plasticity and the Endless Forms of Freshwater Gastropod Shells

Whelan

2021

Freshwater Mollusk Biology and Conservation

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Environmental factors do not contribute significantly to shell shape in the Sprite Elimia, Elimia Proxima (Gastropoda: Pleuroceridae)

Shepard

Minton²

2019

Journal of the Pennsylvania Academy of Science

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Pleurocerid snail diversity has historically been defined by morphological shell features, and these features are believed to be phenotypic responses to environmental factors. More recently, authors have shown the importance of genetics in shell variability, even to the exclusion of any environmental effect. Work by Dillon on Elimia proxima in the 1980s aimed to address this genetic versus environmental correlation of shell features, without reaching a solid conclusion. Using Dillon’s original data and specimens, geometric morphometric analysis was used in a phylogenetic context to show that E. proxima shell variation at the population level is correlated with genetics and not with the environment. This data is the latest example to find that shell variation as the result of environmental factors is too simplistic an explanation in pleurocerids.

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Correlates of snail shell variation along a unidirectional freshwater gradient in Lithasia geniculata (Haldeman, 1840) (Caenogastropoda: Pleuroceridae) from the Duck River, Tennessee, USA

Cited by 4 publications

References 37 publications

Testing the adaptive value of gastropod shell morphology to flow: a multidisciplinary approach based on morphometrics, computational fluid dynamics and a flow tank experiment

Testing the adaptive value of gastropod shell morphology to flow: a multidisciplinary approach based on morphometrics, computational fluid dynamics and a flow tank experiment

Phenotypic Plasticity and the Endless Forms of Freshwater Gastropod Shells

Environmental factors do not contribute significantly to shell shape in the Sprite Elimia, Elimia Proxima (Gastropoda: Pleuroceridae)

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